iStock/Thinkstock(NEW YORK) -- As if battling cancer wasn't enough, many long-term survivors may eventually find themselves dealing with opioid dependency, according to a new study.

Cancer survivors are substantially more likely to be prescribed opioid painkillers over many years, according to research published Monday in the journal Cancer.

Prescription opioids, which are in the same class as illicit heroin, are often indicated and prescribed for pain during cancer treatment and recovery. However, prescription painkillers are difficult to manage over longer term use. Some patients become dependent and develop a tolerance for the drug, requiring increasing doses to get the same pain-killing effect. Ultimately, too much of an opioid medication at once can affect breathing and cause death.

To find out whether very long-term cancer survivors and those who never had cancer were prescribed opioids differently, researchers at the University of Toronto looked at more than 17,000 adults, which included more than 8,600 adult cancer survivors. They compared the group of cancer survivors to others who had never had cancer, but were the same gender and roughly the same age, and found that the cancer survivors were more likely to be prescribed opioids, even up to 10 or more years following their cancer diagnosis.

Younger cancer survivors, those from rural neighborhoods, and those with lower income and more medical problems had an even higher rates of opioid prescriptions. And while researchers can’t say from this study exactly why cancer survivors tend to be more likely to be prescribed painkillers, they highlight a new area of research that could affect how we treat cancer pain.

It’s an important and surprising finding about cancer survivors, according to lead researcher and author of the paper, Rinku Sutradhar, of the University of Toronto’s Department of Biostatistics.

"We thought opioid prescription rates would be similar because we had no reason to believe it would be higher," she said. Sutradhar added that the findings suggest that those making the transition from cancer patients to cancer survivors should keep their new treatment team informed of their opioid use thus far.

"Once you attain survivorship you’re now receiving care form your primary care doctor rather than the oncologist," she said. "During that switch, it would be advisable to inform your primary care physician about everything you experienced, what opioids you took before."

Other experts in the field agreed that the study touches on an important challenge in treating people with chronic pain.

"This article highlights a dilemma about those long-term survivors who are on chronic opioids, and maybe we should take a harder look at them in terms of pain management," said Dr. Charles Shapiro, director of cancer survivorship at the Tisch Cancer Institute at the Icahn School of Medicine at Mount Sinai, who was not involved with this study. "But we often don’t have the resources to take that harder look."

But, he added, it is important not to discount the usefulness of opioids for helping cancer patients manage serious, sometimes debilitating, pain.

"Cancer patients have pain and they take opioids," he said. “We can’t lose the message that opioids are indicated for that group with chronic pain and they work well."

Managing the dosage of opioid prescriptions as years pass after cancer survival is important.

"These are survivors and, although they may have pain, when you’re this far out, they become more like the general population," Shapiro added.

But for many cancer survivors, the return to normalcy is never quite complete. They are often left to deal with a variety of long-term consequences after cancer treatment, which can affect cognition, the heart, bones and the digestive system. Chemotherapy can leave lasting effects on the body; scars and pain are just a few possible complications after surgical treatment; and the psychological effects that can be difficult for patients and their loved ones.

As the opioid epidemic has swept through the nation over the last several decades, the number of opioids prescribed has been a focus of attention. According to the U.S. Centers for Disease Control and Prevention, every day 91 Americans die from a drug overdose. The CDC also estimates that more than half a million people have died of drug overdoses over the last 15 years –- and that the number of opioid deaths in the United States has quadrupled since 1999.

This article was written by Alexa Mieses, M.D., M.P.H., a family medicine resident at Duke University.